Latch-open mechanism for air blast circuit breaker



H. FORWALD July 31, 1962 LATCH-OPEN MECHANISM FOR AIR BLAST CIRCUITBREAKER Filed June 2, 1959 INVENTOR. HAM/v0 Fozmao United States PatentO "ce 3,047,697 LATCH-OPEN MECHANISM FOR AIR BLAST CIRCUIT BREAKERHaakon Forwald, Ludvika, Sweden, assignor to Allmanna Svenska ElektriskaAktiebolaget, Vasteras, Sweden, a

corporation of Sweden Filed June 2, 1959, Ser. No. 817,645 Claimspriority, application Sweden June 4, 1958 Claims. (Cl. 200-148) Thisinvention relates to a contact latch mechanism for pneumaticallyoperated circuit breakers, and more specifically relates to a latchmechanism which latches the contacts open responsive to a decrease inthe air pressure maintaining the contacts open against the force of aclosing spring.

Pneumatically operated circuit breakers are well known where astationary contact is carried in a first housing and the movablecontact, and its operating mechanism is carried in a second housingremovably connected to the first housing. If desired, the first housingcan be under pressure to provide an air blast for extinguishing an aredrawn when the movable contact moves to a disengaged position. Themovable contact is normally biased toward an engaged position by aclosing spring means, and is moved to the open position and held in theopen position by a fluid under pressure, such as air. Although this typeof operating mechanism is extremely desirable because of its inherentsimplicity and reliability, it is possible that air pressure will beunintentionally lost when the contacts are open, so that the closingspring will move the contacts to their engaged position. Thisunintentional closing operation can cause severe damage 'to the breakerand to the components protected thereby, and is a serious hazard tooperating personnel working on the protected lines.

Accordingly, latch means have been provided where a physical latch isconnected to the movable contact responsive to a predetermined loss ofair pressure. This latch mechanism has been connected to the firsthousing which contains the stationary contact structure so that when thelatch is operated, the second housing contain ing the movable contactand its operating mechanism is physically latched to the first housing.Therefore, it is not possible to remove the second housing from thefirst housing for inspection and repair.

The principle of the present invention is to provide a latch mechanismwhich is carried by the second housing containing the movable contactand its operating mechanism so that when the latch operates due to aloss in operating pressure, the housing carrying the latch and themovable contact structure in the latched open position may be removedfor inspection and repair of the pneumatic system or associatedcomponents which have failed. Furthermore, the latch structure may beconstructed to latch the removable contact along its axis whereby theforce exerted by the closing spring against the movable contact will notcause rocking or tilting of the movable contact.

Accordingly, the primary object of this invention is to latch thecontacts of a pneumatically operated circuit interrupter in the openposition responsive to a predetermined loss in operating pressure.

Another object of this invention is to provide a novel latch structurefor pneumatically operated circuit breakers wherein the movable contactis latched open upon the failure of air pressure and the housing,portion containing the latch may be easily disassembled for repair andmaintenance of the mechanism.

A further object of this invention is to provide a latch mechanism for amovable circuit breaker contact which is operated and maintained in thedisengaged position by 3,047,697. Patented July 31, 1962 2 fluidpressure wherein the latch operates responsive to a predetermined lossof air pressure and permits disassembly of the unit.

These and other objects of this invention willbecome apparent from thefollowing description when taken in connection with the drawings, inwhich:

FIGURE 1 shows a side cross-sectional view of one embodiment of thenovel latch structure of the invention in combination with apneumatically operated circuit breaker.

FIGURE 2 shows a detailed view of the latch member carried by themovable contact.

Referring now to the drawings, a first housing 10 is normally filledwith compressed air derived from a com pressed air source 11 which isconnected to housing 10 by conduit 12. Conduit 12 has a valve 13 thereinfor disconnecting housing 10 and source 11. A terminal bushing 14 isconnected at the top of housing 10 in sealed relation and is terminatedat its lower end by a stationary contact 15 connected at the bottom ofthe conductor extending through the terminal bushing 14.

A second housing 16 carries the movable contact structure and itsoperating mechanism and is clamped to the stationary contact housing 10in any desired manner, as by the bolt means 17. Thus, housing 16 carriesa movable nozzle-shaped contact 18 which is connected to a piston means19 by the connecting rod 20. The connecting rod 20 has an extendingportion 21, best seen in FIGURE 2, which is terminated in a bifurcatedportion 22 which carries a pin 23, as shown in FIGURE 2. Rod 20 and pin23 are movable downwardly into engagement with a pawl 24 which ispivotally mounted on pivot 25, and is movable into latching engagementwith pin 23. Thus, rod 20 and its pin 23 form the first portion of alatch mechanism, while pawl 24 forms a second and cooperating portion ofa latch mechanism.

The pawl 24 is driven by a link 26 which is connected to a piston 27carried in cylinder 28 and is movable responsive to the pressure inconduit 30 which is connected to conduit 12. A spring 29 biases piston27 downwardly to move pawl '24 to its latching position, but this motionis normally prevented by the pressure beneath piston 27 from conduit 12.When this pressure fails, however, piston 27 will drop under theinfluence of spring 29 and pawl 24 will move to its latching position.

The movable contact 18 is normally biased to the engaged position shownin FIGURE 1 by closing spring 31 which is seated beneath piston 19 andbiases piston 19 upwardly. In order to move piston '19, and, thus,movable contact 18 to a disengaged position, a valve 32 is movable toconnect the upper area 33 adjacent the top of the cylinder containingpiston 19 to the pressure of conduit 12 over the conduit 34. The lowersurface of piston 19 is connected to the external pressure oratmospheric pressure.

Accordingly, when valve 32 connects conduit 12 to conduit 34, thepressure in volume 33 increases to overcome the spring force of closingspring 31 so that the contacts are driven to their disengaged position.

Although it is not necessary for purposes of the instant invention, theair blast action during contact disengagement may be noted. Prior toopening, the upper end of the movable contact is sealed to thestationary contact in air tight relation. During the opening operation,however, this seal is defeated and the compressed air contained inhousing 10 will be forced through the centre of the movable contact andthrough the arc, and then through check valve means 35. The air blastacross the opening contacts is continued until piston 19 drops tocloseoff check valve 35. The movable contact will thereafter he held-open bythe high pressure of volume 33 which imparts a greater force to the topof piston 19 than does the spring 31 to the bottom of piston 19.

In order to close the circuit breaker, valve 32 is operated so thatconduit 34 is vented to the external air whereby the pressure in volume33 decreases and the spring force of spring 31 closes the contacts.

In accordance with the present invention, when the movable contact 18 isheld in its disengaged position by means of the high pressure in volume33, the mechanical latch including pawl 24 will be disengaged. When, however, there is a leak, or the pressure of source 11 decreases below apredetermined value so that there may be an unintentional closing of themovable contact, the piston 27 will drop before the spring 31 can drivethe contacts closed, whereby pawl 24 will engage pin 23 to latch thecontacts open. Thereafter, a complete loss of air pressure will beincapable of closing the movable contact against the latch mechanism.When pressure is returned, the piston 27 will be driven upwardly torelease this latching engagement so that normal operation can proceed.

Since the latch mechanism is carried in the movable contact housing,although the movable contact is latched open under low pressureconditions, the housing 16 can be removed from housing so that themechanism may be inspected and repaired. This is to be contrasted to theprevious types of pressure responsive latches wherein the latchmechanism formed a connection between housings, such as housing 10, andthe lower housing 16, so that the disconnection of the housings was notpossible.

Furthermore, the latch mechanism operates along the axis of the movablecontact. Therefore, when contact rod is latched open, it will not betilted by the force of closing spring 31.

Although the invention has been described with respect to its preferredembodiments it should be understood that many variations andmodifications will now be obvious to those skilled in the art, and it ispreferred, therefore, that the scope of this invention be limited not bythe specific disclosure herein but only by the appended claims.

What is claimed is:

l. A latch mechanism for a pneumatically operated circuit breaker; saidpneumatically operated circuit breaker including a first and secondhousing, said first housing being removably connected to said secondhousing, said first housing carrying a first contact, said secondhousing carrying a second contact movable between an engaged anddisengaged position with respect to said first contact when said firsthousing is connected to said second housing, a pneumatic operating meansfor moving and maintaining said second contact out of engagement withrespect to said first contact, a source of air under pressure,connections from such source to said pneumatic operating means and tosaid first housing, a valve in said connection to said pneumaticoperating means, latch means engageable with said movable contact andmovable to a latching position to latch said movable contact in saiddisengaged position, and means operatively connected to said latch meansand responsive to a predetermined pressure condition in said compressedair source to move said latch means to latching position upon the dropof pressure in said first housing below a predetermined pressure and tomove said latch means to unlatching position upon a rise of pressure insaid first housing above said predetermined pressure.

2. A latch mechanism for a pneumatically operated circuit breaker, saidpneumatically operated circuit breaker including a first and secondhousing, said first housing being removably connected to said secondhousing, said first housing carrying a first contact, said secondhousing carrying a second contact movable between an engaged anddisengaged position with respect to said first contact when said firsthousing is connected to said second housing, a pneumatic operating meansfor moving and maintaining said second contact out of engagement withrespect to said first contact, a source of air under pressure,connections from such source to said pneumatic operating means and tosaid first housing, a valve in said connection to said pneumaticoperating means, latch means engageable with said movable contact andmovable to a latching position to latch said movable contact in saiddisengaged position, and means operatively connected to said latch meansand responsive to a predetermined pressure condition in said compressedair source to move said latch means to latching position upon the dropof pressure in said first housing below a predetermined pressure and tomove said latch means to unlatching position upon a rise of pressure insaid first housing above said predetermined pressure, said latch meansbeing carried by said second housing.

3. A latch mechanism for a pneumatically operated circuit breaker, saidpneumatically operated circuit breaker including a first and secondhousing, said first housing being removably connected to said secondhousing, said first housing carrying a first contact, said secondhousing carrying a second contact movable between an engaged anddisengaged position with respect to said first contact when said firsthousing is connected to said second housing, a pneumatic operating meansfor moving and maintaining said second contact out of engagement withrespect to said first contact, a source of air under pressure,connections from such source to said pneumatic operating means and tosaid first housing, a valve in said connection to said pneumaticoperating means, latch means engageable with said movable contact andmovable to a latching position to latch said movable contact in saiddisengaged position, and means operatively connected to said latch meansand responsive to a predetermined pressure condition in said compressedair source to move said latch means to latching position upon the dropof pressure in said first housing below a predetermined pressure and tomove said latch means to unlatching position upon a rise of pressure insaid first housing above said predetermined pressure, said latch meansbeing carried by said second housing, said first and second housingsbeing removable when said latch means is in said latching position.

4. A latch mechanism for a pneumatically operated circuit breaker, saidpneumatically operated circuit breaker including a first and secondhousing, said first housing being removably connected to said secondhousing, said first housing carrying a first contact, said secondhousing carrying a second contact movable between an engaged anddisengaged position with respect to said first contact when said firsthousing is connected to said second housing, a pneumatic operating meansfor moving and maintaining said second contact out of engagement withrespect to said first contact, a source of air under pressure,connections from such source to said pneumatic operating means and tosaid first housing, a valve in said connection to said pneumaticoperating means, latch means engageable with said movable contact andmovable to a latching position to latch said movable contact in saiddisengaged position, and means operatively connected to said latch meansand responsive to a predetermined pressure condition in said compressedair source to move said latch means to latching position upon the dropof pressure in said first housing below a predetermined pressure and tomove said latch means to unlatching position upon a rise of pressure insaid first housing above said predetermined pressure, said secondcontact operating means including means for moving said second contactalong an axis to said engaged position, said latching means engagingsaid movable contact along said axis.

5. A latch mechanism for a pneumatically operated circuit breaker, saidpneumatically operated circuit breaker including a first and secondhousing, said first housing being removably connected to said secondhousing, said first housing carrying a first contact, said secondhousing carrying a second contact movable between an engaged anddisengaged position with respect to said first contact when said firsthousing is connected to said second housing, a pneumatic operating meansfor moving and maintaining said second contact out of engagement withrespect to said first contact, a source of air under pressure,connections from such source to said pneumatic operating means and tosaid first housing, a valve in said connection to said pneumaticoperating means, latch means engageable with said movable contact andmovable to a latching position to latch said movable contact in saiddisengaged position, and means operatively connected to said latch meansand responsive to a predetermined pressure condition in said compressedair source to move said latch means to latching position upon the dropof pressure in said first housing below a predetermined pressure and tomove said latch means to unlatching position upon a rise of pressure insaid first housing above said predetermined pressure, said secondcontact operating means including means for moving said second contactalong an axis to said engaged position, said latching means engagingsaid movable contact along said axis, said latch means being carried bysaid second housing, said first and second housings being removable whensaid latch means is in said latching position.

6. In a pneumatically operated circuit breaker, a housing, a relativelystationary contact and a relatively movable contact in said housing, andan operating mechanism for said relatively movable contact, a firstoperating means for moving said relatively movable contact intoengagement with respect to said relatively stationary contact and asecond operating means for moving said relatively movable contact to adisengaged position with respect to said relatively stationary contact,said second operating means comprising a piston means operativelyconnected to said relatively movable contact and pneumatic pressuremeans for moving said piston, a source of air under pressure,connections from said source to said pneumatic pressure means, a valvein said connection to said pneumatic pressure means, a latch mechanismoperatively engageable with said movable contact, said latch mechanismbeing movable to a latching position to latch said relatively movablecontact in said disengaged position, said latch mechanism being operableresponsive to variations in the pressure of said pneumatic pressuremeans to move the latch mechanism to latching position upon the drop ofpressure in said compressed air source below a pre-determined airpressure and to move the latch mechanism to unlatching position upon arise in pressure of said housing above said predetermined pressure.

7. In a pneumatically operated circuit breaker, a housing, a relativelystationary contact and a relatively movable contact in said housing, andan operating mechanism for said relatively movable contact, a firstoperating means for moving said relatively movable contact intoengagement with respect to said relatively stationary contact and asecond operating means for moving said relatively movable contact to adisengaged position with respect to said relatively stationary contact,said second operating means comprising a piston means operativelyconnected to said relatively movable contact and pneumatic pressuremeans for moving said piston, a source of air under pressure,connections from said source to said pneumatic pressure means, a valvein said connection to said pneumatic pressure means, a latch mechanismoperatively engageable with said movable contact, said latch mechanismbeing movable to a latching position to latch said relatively movablecontact in said disengaged position, said latch mechanism being operableresponsive to variations in the pressure of said pneumatic pressuremeans to move the latch mechanism to latching position upon the drop ofpressure in said compressed air source below a predetermined airpressure and to move the latch mechanism to unlatching position upon arise in pressure of said housing above said predetermined pressure, saidlatch mechanism being mounted independently of said relatively movablecontact. I

8. In a pneumatically operated circuit breaker, a housing, a relativelystationary contact and a relatively movable contact in said housing, andan operating mechanism for said relatively movable contact, a firstoperating means for moving said relatively movable contact intoengagement with respect to said relatively stationary contact and asecond operating means for moving said relatively movable contact to adisengaged position with respect to said relatively stationary contact,said second operating means comprising -a piston means operativelyconnected to said relatively movable contact and pneumatic pressuremeans for moving said piston, a source of air under pressure,connections from said source to said pneumatic pressure means, a valvein said connection to said pneumatic pressure means, a latch mechanismoperatively engageable with said movable contact, said latch mechanismbeing movable to a latching position to latch said relatively movablecontact in said disengaged position, said latch mechanism being operableresponsive to variations in the pressure of said pneumatic pressuremeans to move the latch mechanism to latching position upon the drop ofpressure in said compressed air source below a pre-determined airpressure and to move the latch mechanism to unlatching position upon arise in pressure of said housing above said predetermined pressure, saidlatch mechanism being mounted independently of said relatively movablecontact, said first operating means comprising spring means engagingsaid piston means.

9. In -a pneumatically operated circuit breaker, a housing, a relativelystationary contact and a relatively movable contact in said housing, andan operating mechanism for said relatively movable contact, a firstoperating means for moving said relatively movable contact intoengagement with respect to said relatively stationary contact and asecond operating means for moving said relatively movable contact to adisengaged position with respect to said relatively stationary contact,said second operating means comprising a piston means operativelyconnected to said relatively movable contact and pneumatic pressuremeans for moving said piston, a source of air under pressure,connections from said source to said pneumatic pressure means, a valvein said connection to said pneumatic pressure means, a latch mechanismoperatively engageable with said movable contact, said latch mechanismbeing movable to a latching position to latch said relatively movablecontact in said disengaged position, said latch mechanism being operableresponsive to variations in the pressure of said pneumatic pressuremeans to move the latch mechanism to latching position upon the drop ofpressure in said compressed air source below a pre-determined airpressure and to move the latch mechanism to unlatching position upon arise in pressure of said housing above said predetermined pressure, saidoperative connection between said relatively movable contact and saidpiston including rod means having a portion extending through saidpiston means, said latch means engaging said extending portion of saidrod means at a point along its axis.

10. In a pneumatically operated circuit breaker, a housing, a relativelystationary contact and a relatively movable contact in said housing, andan operating mechanism for said relatively movable contact, a firstoperating means for moving said relatively movable contact intoengagement with respect to said relatively stationary contact and asecond operating means for moving said relatively movable contact to adisengaged position with respect to said relatively stationary contact,said second operating means comprising a piston means operativelyconnected to said relatively movable contact and pneumatic pressuremeans for moving said piston, a source of air under pressure,connections from said source to said pneumatic pressure means, a valvein said connection to said pneumatic pressure means, a latch mechanismoperatively engageable with said movable contact, said latch mechanismbeing movable to a latching position to latch said relatively movablecontact in said disengaged position, said latch mechanism being operableresponsive to variations in the pressure of said pneumatic pressuremeans to move the Latch mechanism to latching position upon the drop ofpressure in said compressed air source below a pre-determined airpressure and to move the latch mechanism to unlatching position upon arise in pressure of said housing above said predetermined pressure, saidoperative connection between said relatively movable I contact and saidpiston including rod means having a portion extending through saidpiston means, said latch means engaging said extending portion of saidrod means at a point along its axis, said latch mechanism being 8mounted independently ofsaid relatively movable contact.

References Cited in the file of this patent UNITED STATES PATENTS859,843 Rogers July 9, 1907 1,129,878 Lucker et al Mar. 2, 19152,660,636 Wallace Nov. 24, 1953 2,824,937 Strom Feb. 25, 1958 2,856,480Westerhofi Oct. 14, 1958 2,911,492 Beatty NOV. 3, 1959 2,936,355 CaswellMay 10, 1960 2,949,521 Schulz Aug. 16, 1 960 2,972,666 Forwald Feb. 21,1961 FOREIGN PATENTS 512,623 Great Britain Sept. 21, 1939 1,005,155Germany Mar. 28, 1957 608,733 Germany Jan. 31, 1938

